AFAIK, push notifications require a Google account to work (they piggyback on GTalk), so does that mean for apps for the Kindle Fire are doomed if they use the standard C2DM
Note that Urban Airship ended support for Helium for Google Android - their custom technology that allowed push notifications to Kindle and NOOK devices (Helium For Google Android Sunset FAQ).
Here (Google Cloud Messaging Support FAQ) they do state:
"We plan to support Kindle via Amazon's Amazon Device Messaging (ADM) service at some point in the future."